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banners=-,-,- X-VirusChecked: Checked From: Huaisheng HS1 Ye To: Matthew Wilcox CC: "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "mhocko@suse.com" , "vbabka@suse.cz" , "mgorman@techsingularity.net" , "alexander.levin@verizon.com" , "colyli@suse.de" , NingTing Cheng , "linux-kernel@vger.kernel.org" Subject: RE: [External] Re: [PATCH v1] include/linux/gfp.h: getting rid of GFP_ZONE_TABLE/BAD Thread-Topic: [External] Re: [PATCH v1] include/linux/gfp.h: getting rid of GFP_ZONE_TABLE/BAD Thread-Index: AQHT6HxSRcNgfj0RT02kxPWBEx8Dn6Qp2QqggACtQICACkWf8A== Date: Fri, 18 May 2018 03:03:35 +0000 Message-ID: References: <1525968625-40825-1-git-send-email-yehs1@lenovo.com> <20180510163023.GB30442@bombadil.infradead.org> <20180511132613.GA30263@bombadil.infradead.org> In-Reply-To: <20180511132613.GA30263@bombadil.infradead.org> Accept-Language: zh-CN, en-US Content-Language: zh-CN X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [114.245.9.79] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;HK2PR03MB0706;7:SmQlXtAUTsnKJ099R3kgCU5wtrDRyZkbUf0K3Yo2MT1JoX4bjVWjQ2NT79Tlnis+H1XnQ0+C46ekQNbOkHZ07bW7s5Pb8fFff7dfC299HPat9ZsgLmkZVRf+7uytXmzeTZAv/+85AjSjqu/9o9otG9nDnVUrNDwXEt5RUK8UjzuQiWlBHDoqakWq1mV8eg/xZtYsEWvInkd8kSnBDrDhj/Qaf++/LK9uGeOrJW8tLJCfCk5ETpPfzpdXVdt8CTYd;20:23c2ZTXNbo57iRbuYsfIYItpjSEoezwndyz01hbWnaiPXagF0CabgDsSQJhlEfqAFXb+W7/8k1YeTzMZwgUZJYRK9nFbP0LF6ZjmNDUI0TfCP4Z3+N3MsMEig77XLTdXq+jSEVsXZ0OUIb9cjpvmTSE2FxU7+wiIJU9GGmoqJ2Rk2DbwYb4ConxLx/TogZl/JDl0g9Kc+LIfqpuAZV63BEoPF1q3n/8kXCtuKq6Q1M5AiJiH2K+x/7FQ06nUQixHaWofO2lm8Zwlbfo9zWMcxl8QQnpKrg/QmT9eXfzvPHkGuh+4+Y+0UJZGHyBJYdXSAvipbjTkcZC5fojnbHtmEg== x-ms-exchange-antispam-srfa-diagnostics: SOS;SOR; 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x-ms-exchange-senderadcheck: 1 x-exchange-antispam-report-cfa-test: BCL:0;PCL:0;RULEID:(6040522)(2401047)(5005006)(8121501046)(10201501046)(3002001)(3231254)(944501410)(52105095)(93006095)(93001095)(149027)(150027)(6041310)(201703131423095)(201702281528075)(20161123555045)(201703061421075)(201703061406153)(20161123560045)(20161123564045)(20161123558120)(20161123562045)(6072148)(201708071742011)(7699016);SRVR:HK2PR03MB0706;BCL:0;PCL:0;RULEID:;SRVR:HK2PR03MB0706; x-forefront-prvs: 0676F530A9 x-microsoft-antispam-message-info: 82s7sLTsgx7IA3vCwZBe5MxDY8ksOy/eXcqUgNnteq33rCJdmEh57QEG1w2kZZHF5UUnln6sPoHGBOyOxmCRjVoMAEaX5lZNgZKMMaR+2yqZeIdDIpIY1dV9z6P/Yj4fspHdE0h5bwOzVnDfNcfdKRuad423/o8zczywbnqalqPtwkpt12sNOXGm3/QWoSH/ spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 X-MS-Office365-Filtering-Correlation-Id: bf6dc84f-80b6-4f4b-1ede-08d5bc6bf25e X-MS-Exchange-CrossTenant-Network-Message-Id: bf6dc84f-80b6-4f4b-1ede-08d5bc6bf25e X-MS-Exchange-CrossTenant-originalarrivaltime: 18 May 2018 03:03:35.4695 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 5c7d0b28-bdf8-410c-aa93-4df372b16203 X-MS-Exchange-Transport-CrossTenantHeadersStamped: HK2PR03MB0706 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id w4I34AF8000468 > From: Matthew Wilcox [mailto:willy@infradead.org] > Sent: Friday, May 11, 2018 9:26 PM > On Fri, May 11, 2018 at 03:24:34AM +0000, Huaisheng HS1 Ye wrote: > > > From: owner-linux-mm@kvack.org [mailto:owner-linux-mm@kvack.org] On Behalf Of > Matthew > > > Wilcox > > > On Fri, May 11, 2018 at 12:10:25AM +0800, Huaisheng Ye wrote: > > > > -#define __GFP_DMA ((__force gfp_t)___GFP_DMA) > > > > -#define __GFP_HIGHMEM ((__force gfp_t)___GFP_HIGHMEM) > > > > -#define __GFP_DMA32 ((__force gfp_t)___GFP_DMA32) > > > > +#define __GFP_DMA ((__force gfp_t)OPT_ZONE_DMA ^ ZONE_NORMAL) > > > > +#define __GFP_HIGHMEM ((__force gfp_t)ZONE_MOVABLE ^ ZONE_NORMAL) > > > > +#define __GFP_DMA32 ((__force gfp_t)OPT_ZONE_DMA32 ^ ZONE_NORMAL) > > > > > > No, you've made gfp_zone even more complex than it already is. > > > If you can't use OPT_ZONE_HIGHMEM here, then this is a waste of time. > > > > > Dear Matthew, > > > > The reason why I don't use OPT_ZONE_HIGHMEM for __GFP_HIGHMEM directly is that, > for x86_64 platform there is no CONFIG_HIGHMEM, so OPT_ZONE_HIGHMEM shall always be > equal to ZONE_NORMAL. > > Right. On 64-bit platforms, if somebody asks for HIGHMEM, they should > get NORMAL pages. > > > For gfp_zone it is impossible to distinguish the meaning of lowest 3 bits in flags. > How can gfp_zone to understand it comes from OPT_ZONE_HIGHMEM or ZONE_NORMAL? > > And the most pained thing is that, if __GFP_HIGHMEM with movable flag enabled, it > means that ZONE_MOVABLE shall be returned. > > That is different from ZONE_DMA, ZONE_DMA32 and ZONE_NORMAL. > > The point of this exercise is to actually encode the zone number in > the bottom bits of the GFP flags instead of something which has to be > interpreted into a zone number. When somebody sets __GFP_MOVABLE, they > should also be setting ZONE_MOVABLE: > > -#define __GFP_MOVABLE ((__force gfp_t)___GFP_MOVABLE) /* ZONE_MOVABLE allowed */ > +#define __GFP_MOVABLE ((__force gfp_t)(___GFP_MOVABLE | (ZONE_MOVABLE ^ ZONE_NORMAL))) > > One thing that does need to change is: > > -#define GFP_HIGHUSER_MOVABLE (GFP_HIGHUSER | __GFP_MOVABLE) > +#define GFP_HIGHUSER_MOVABLE (GFP_USER | __GFP_MOVABLE) > > otherwise we'll be OR'ing ZONE_MOVABLE and ZONE_HIGHMEM together. Dear Matthew, After thinking it over and over, I am afraid there is something needs to be discussed here. You know current X86_64 config file of kernel doesn't enable CONFIG_HIGHMEM, that is to say from this below, #define __GFP_HIGHMEM ((__force gfp_t)OPT_ZONE_HIGHMEM ^ ZONE_NORMAL) __GFP_HIGHMEM should equal to 0b0000, same as the value of ZONE_NORMAL gets encoded. If we define __GFP_MOVABLE like this, #define __GFP_MOVABLE ((__force gfp_t)(___GFP_MOVABLE | (ZONE_MOVABLE ^ ZONE_NORMAL))) Just like your introduced before, with this modification when somebody sets __GFP_MOVABLE, they should also be setting ZONE_MOVABLE. That brings us a problem, current mm (GFP_ZONE_TABLE) treats __GFP_MOVABLE as ZONE_NORMAL with movable policy, if without __GFP_HIGHMEM. The mm shall allocate a page or pages from migrate movable list of ZONE_NORMAL's freelist. So that conflicts with this modification. And I have checked current kernel, some of function directly set parameter gfp like this. For example, in fs/ext4/extents.c __read_extent_tree_block, bh = sb_getblk_gfp(inode->i_sb, pblk, __GFP_MOVABLE | GFP_NOFS); for these situations, I think only modify GFP_HIGHUSER_MOVABLE is not enough. I am preparing a workaround to solve this in the V2 patch. Later I will upload it to email loop. Sincerely, Huaisheng Ye > > I was thinking... > > Whether it is possible to use other judgement condition to decide OPT_ZONE_HIGHMEM > or ZONE_MOVABLE shall be returned from gfp_zone. > > > > Sincerely, > > Huaisheng Ye > > > > > > > > static inline enum zone_type gfp_zone(gfp_t flags) > > > > { > > > > enum zone_type z; > > > > - int bit = (__force int) (flags & GFP_ZONEMASK); > > > > + z = ((__force unsigned int)flags & ___GFP_ZONE_MASK) ^ ZONE_NORMAL; > > > > + > > > > + if (z > OPT_ZONE_HIGHMEM) > > > > + z = OPT_ZONE_HIGHMEM + > > > > + !!((__force unsigned int)flags & ___GFP_MOVABLE); > > > > > > > > - z = (GFP_ZONE_TABLE >> (bit * GFP_ZONES_SHIFT)) & > > > > - ((1 << GFP_ZONES_SHIFT) - 1); > > > > - VM_BUG_ON((GFP_ZONE_BAD >> bit) & 1); > > > > + VM_BUG_ON(z > ZONE_MOVABLE); > > > > return z; > > > > } > >